Except for the known deficiencies with the ASDE in the tower, no equipment failure issues were involved in this occurrence. However, the procedures that were in place did not prevent the controller from losing track of aircraft positioning. Furthermore, the remaining defences did not provide sufficient backup after the controller mistakenly assumed that Jazz 8191 was behind Navair612. The factors that led to the controller making an incorrect assumption about the position of Jazz8191 were as follows: Taxiway L2 had been closed during the south tower controller's previous night shift. The controller did not register that Taxiway L2 was open even though it was not blocked out on the ASDE monitor at his workstation to indicate that it was closed, and despite his daily pre-shift review on the day of the occurrence and during the previous four day shifts. When the south tower controller observed an ASDE target at TaxiwayL2, he assumed the target to be false because of the previously noted unreliability of the ASDE equipment. The south tower controller did not verify the target at TaxiwayL2 with the available binoculars, radio communications, or the south ground controller. The displaced and partially obscured taxiway assignment, L2,on the flight progress strip for Jazz 8191 resulted in the south tower controller missing the digit 2 when he scanned down the column of flight progress strips. Even though multiple defences may apply to one party, if that party is a party of one and an error is introduced, biases3 may prevent recognition and acceptance of information that is contrary to the party's mental model or mindset of the current situation. In this occurrence, the south tower controller's plan was based on false information, and, although cues to the contrary were present, those cues did not cause the south tower controller to re-evaluate the situation. Defences, common to two or more parties, were also in place to prevent such runway incursions: Neither the south tower controller nor the pilots of either aircraft on the runway stated runway locations. When clearing an aircraft onto a runway from a position other than the threshold, controllers are required to state the runway entry location. A runway entry location was not communicated to Jazz8191 because the south tower controller believed that Jazz 8191 was at the threshold. In this instance, there may have been an obligation for the flight crew of Jazz8191 to query the south tower controller because they could not see the Navair Islander that they had been cleared to position behind, and because their clearance did not mention the intersection entry point (as stated in the AIM). The runway entry location for Navair612 was not stated, nor was it required at the threshold. The lack of a communicated runway entry location for Navair612 did not necessarily create an expectation for the crew of Jazz8191 that the Islander was at the threshold behind them. The circumstances of this occurrence demonstrate that the safety action taken by NAV CANADA in response to TSB investigation A00P0206 fell short of being complete because it did not establish a requirement for tower controllers to also state runway entry locations at the threshold when intersection departure procedures are being used. Furthermore, pilots are not required to state the position at which they will enter a runway or commence their take-off roll. These shortfalls continue to contribute to confusion and erroneous assumptions. The result is a continuing risk of collision from runway incursions when intersection departure procedures are being used. It has long been argued that a common frequency and common phraseology act as a safety defence by promoting a heightened level of situational awareness among all users. However, the chance of identifying and correcting an error, through the use of radio protocols, is also directly dependent on the rigour with which those protocols are applied. During the communication exchange regarding the navigation lights on an Islander, the unidentified transmission from the DHC-8 behind the Islander reinforced the south tower controller's perception that events were being executed in accordance with his plan, when, in fact, they were not. The use of proper call signs could have alerted the south tower controller that the DHC-8 behind the Islander was not Jazz8191. Of six flight crews in a position to monitor the south tower control frequency, many of which were two-pilot operations, no one queried the south tower controller about the location of the DHC-8 (Jazz8191) that was instructed to line up behind the Islander. This factor may indicate that no one really had an accurate awareness of the situation and confusion therefore prevailed. There were no weather-related obstructions to visibility on the airfield, and yet the sole pilot of Navair612 did not see the DHC-8 until passing by it during rotation for lift-off. A take-off clearance indicates to a pilot that the runway surface is clear of traffic and safe for the intended operation; therefore, a pilot would not expect to see an aircraft on the runway ahead. The south tower controller's focus on planning ahead for several departures and other potential workload distractions likely made it more difficult for the south tower controller to detect, by visual means alone, that Jazz8191 had moved onto the runway (unexpectedly from the controller's perspective) at TaxiwayL2. It is reasonable to conclude that darkness, distance, airport and aircraft lighting, and the angle of approach to the runway for Jazz8191 adversely affected the ability of the flight crews and tower controller to clearly see the correct traffic model. Much has also been written about the limitations of the human eye regarding unalerted see-and-avoid in mid-air collisions and air proximity events. These same limitations may have played a role in this occurrence. The risk of a runway incursion is increased when aircraft approach the active runway from positions other than the threshold, rather than in a single line at the threshold. Once an error (unexpected event) occurs, compounded by adverse visibility, the chance of the error being noticed is reduced. Because flight crews are not required to include the taxiway or runway intersection with clearance onto a runway and because tower controllers are not required to include the entry point in clearances at the threshold, risk in the runway environment is increased during intersection departure operations, especially at night or during low-visibility operations.Analysis Except for the known deficiencies with the ASDE in the tower, no equipment failure issues were involved in this occurrence. However, the procedures that were in place did not prevent the controller from losing track of aircraft positioning. Furthermore, the remaining defences did not provide sufficient backup after the controller mistakenly assumed that Jazz 8191 was behind Navair612. The factors that led to the controller making an incorrect assumption about the position of Jazz8191 were as follows: Taxiway L2 had been closed during the south tower controller's previous night shift. The controller did not register that Taxiway L2 was open even though it was not blocked out on the ASDE monitor at his workstation to indicate that it was closed, and despite his daily pre-shift review on the day of the occurrence and during the previous four day shifts. When the south tower controller observed an ASDE target at TaxiwayL2, he assumed the target to be false because of the previously noted unreliability of the ASDE equipment. The south tower controller did not verify the target at TaxiwayL2 with the available binoculars, radio communications, or the south ground controller. The displaced and partially obscured taxiway assignment, L2,on the flight progress strip for Jazz 8191 resulted in the south tower controller missing the digit 2 when he scanned down the column of flight progress strips. Even though multiple defences may apply to one party, if that party is a party of one and an error is introduced, biases3 may prevent recognition and acceptance of information that is contrary to the party's mental model or mindset of the current situation. In this occurrence, the south tower controller's plan was based on false information, and, although cues to the contrary were present, those cues did not cause the south tower controller to re-evaluate the situation. Defences, common to two or more parties, were also in place to prevent such runway incursions: Neither the south tower controller nor the pilots of either aircraft on the runway stated runway locations. When clearing an aircraft onto a runway from a position other than the threshold, controllers are required to state the runway entry location. A runway entry location was not communicated to Jazz8191 because the south tower controller believed that Jazz 8191 was at the threshold. In this instance, there may have been an obligation for the flight crew of Jazz8191 to query the south tower controller because they could not see the Navair Islander that they had been cleared to position behind, and because their clearance did not mention the intersection entry point (as stated in the AIM). The runway entry location for Navair612 was not stated, nor was it required at the threshold. The lack of a communicated runway entry location for Navair612 did not necessarily create an expectation for the crew of Jazz8191 that the Islander was at the threshold behind them. The circumstances of this occurrence demonstrate that the safety action taken by NAV CANADA in response to TSB investigation A00P0206 fell short of being complete because it did not establish a requirement for tower controllers to also state runway entry locations at the threshold when intersection departure procedures are being used. Furthermore, pilots are not required to state the position at which they will enter a runway or commence their take-off roll. These shortfalls continue to contribute to confusion and erroneous assumptions. The result is a continuing risk of collision from runway incursions when intersection departure procedures are being used. It has long been argued that a common frequency and common phraseology act as a safety defence by promoting a heightened level of situational awareness among all users. However, the chance of identifying and correcting an error, through the use of radio protocols, is also directly dependent on the rigour with which those protocols are applied. During the communication exchange regarding the navigation lights on an Islander, the unidentified transmission from the DHC-8 behind the Islander reinforced the south tower controller's perception that events were being executed in accordance with his plan, when, in fact, they were not. The use of proper call signs could have alerted the south tower controller that the DHC-8 behind the Islander was not Jazz8191. Of six flight crews in a position to monitor the south tower control frequency, many of which were two-pilot operations, no one queried the south tower controller about the location of the DHC-8 (Jazz8191) that was instructed to line up behind the Islander. This factor may indicate that no one really had an accurate awareness of the situation and confusion therefore prevailed. There were no weather-related obstructions to visibility on the airfield, and yet the sole pilot of Navair612 did not see the DHC-8 until passing by it during rotation for lift-off. A take-off clearance indicates to a pilot that the runway surface is clear of traffic and safe for the intended operation; therefore, a pilot would not expect to see an aircraft on the runway ahead. The south tower controller's focus on planning ahead for several departures and other potential workload distractions likely made it more difficult for the south tower controller to detect, by visual means alone, that Jazz8191 had moved onto the runway (unexpectedly from the controller's perspective) at TaxiwayL2. It is reasonable to conclude that darkness, distance, airport and aircraft lighting, and the angle of approach to the runway for Jazz8191 adversely affected the ability of the flight crews and tower controller to clearly see the correct traffic model. Much has also been written about the limitations of the human eye regarding unalerted see-and-avoid in mid-air collisions and air proximity events. These same limitations may have played a role in this occurrence. The risk of a runway incursion is increased when aircraft approach the active runway from positions other than the threshold, rather than in a single line at the threshold. Once an error (unexpected event) occurs, compounded by adverse visibility, the chance of the error being noticed is reduced. Because flight crews are not required to include the taxiway or runway intersection with clearance onto a runway and because tower controllers are not required to include the entry point in clearances at the threshold, risk in the runway environment is increased during intersection departure operations, especially at night or during low-visibility operations. When Navair 612, at the threshold of Runway 08R, received the clearance for take-off, the runway was unsafe for the intended operation because another aircraft, Jazz8191, was taxiing, in accordance with air traffic control (ATC) instructions, to position on the same runway. Unbeknownst to the crew of either aircraft on the runway or to the south tower controller, Jazz8191 was in front of Navair612, rather than behind, as assumed. Cues to contradict the south tower controller's assumption that TaxiwayL2 was closed were present, but those cues did not cause the controller to re-evaluate the situation. The south tower controller did not use the binoculars, radio communications, or the south ground controller at the adjacent workstation to verify the airport surface detection equipment (ASDE) target displayed at TaxiwayL2. The taxiway assignment, L2,was displaced and partially obscured on the flight progress strip for Jazz8191. The digit 2was not detected when the south tower controller scanned down the column of flight progress strips. The instruction for Jazz8191 to taxi to position on Runway08R did not include the taxiway designator, as would be required for an intersection departure. This missing segment of the instruction was not questioned by the flight crew, and an opportunity was missed to alert the south tower controller that his plan was not being executed as intended. A series of unidentified radio transmissions occurred regarding inoperative navigation lights on an Islander, creating some confusion. Some of these transmissions reinforced the south tower controller's belief that his plan was being executed as intended when, in fact, it was not.Findings as to Causes and Contributing Factors When Navair 612, at the threshold of Runway 08R, received the clearance for take-off, the runway was unsafe for the intended operation because another aircraft, Jazz8191, was taxiing, in accordance with air traffic control (ATC) instructions, to position on the same runway. Unbeknownst to the crew of either aircraft on the runway or to the south tower controller, Jazz8191 was in front of Navair612, rather than behind, as assumed. Cues to contradict the south tower controller's assumption that TaxiwayL2 was closed were present, but those cues did not cause the controller to re-evaluate the situation. The south tower controller did not use the binoculars, radio communications, or the south ground controller at the adjacent workstation to verify the airport surface detection equipment (ASDE) target displayed at TaxiwayL2. The taxiway assignment, L2,was displaced and partially obscured on the flight progress strip for Jazz8191. The digit 2was not detected when the south tower controller scanned down the column of flight progress strips. The instruction for Jazz8191 to taxi to position on Runway08R did not include the taxiway designator, as would be required for an intersection departure. This missing segment of the instruction was not questioned by the flight crew, and an opportunity was missed to alert the south tower controller that his plan was not being executed as intended. A series of unidentified radio transmissions occurred regarding inoperative navigation lights on an Islander, creating some confusion. Some of these transmissions reinforced the south tower controller's belief that his plan was being executed as intended when, in fact, it was not. Neither the south tower controller nor the pilots of either aircraft on the runway stated runway locations. These shortfalls continue to contribute to confusion and erroneous assumptions, with a continuing risk of collision from runway incursions being the result. Tower controllers are not required to include the entry point in clearances onto the runway at the threshold and flight crews are not required to indicate the taxiway or runway intersection entry point onto a runway. Therefore, the risk of a runway incursion error is increased during intersection departure operations, especially at night or during low-visibility operations. The ASDE system at Vancouver International Airport has been known to randomly display erroneous information, which places an additional workload upon controllers to verify airfield traffic by other means.Findings as to Risk Neither the south tower controller nor the pilots of either aircraft on the runway stated runway locations. These shortfalls continue to contribute to confusion and erroneous assumptions, with a continuing risk of collision from runway incursions being the result. Tower controllers are not required to include the entry point in clearances onto the runway at the threshold and flight crews are not required to indicate the taxiway or runway intersection entry point onto a runway. Therefore, the risk of a runway incursion error is increased during intersection departure operations, especially at night or during low-visibility operations. The ASDE system at Vancouver International Airport has been known to randomly display erroneous information, which places an additional workload upon controllers to verify airfield traffic by other means. As Jazz 8191 was proceeding onto the runway, the crew became uneasy and decided to stop and turn to their right to view the runway toward the threshold. This single action was the last remaining defence against a collision on the runway.Other Findings As Jazz 8191 was proceeding onto the runway, the crew became uneasy and decided to stop and turn to their right to view the runway toward the threshold. This single action was the last remaining defence against a collision on the runway. The Vancouver International Airport tower manager issued an Operations Bulletin on 04November2004 to remind controllers to adhere to the Air Traffic Control Manual of Operations (ATC MANOPS) direction to state the name of the intersection or taxiway when issuing taxi to position instructions or take-off clearances from an intersection. Controllers were also encouraged to specify the threshold used if more than one aircraft was being taxied to position. The Vancouver Control Tower Operations Committee conducted a review of the Operations Bulletin before its expiry date and a decision was made to let it expire without implementing any new procedure. The Vancouver International Airport tower manager issued direction to tower staff to document any anomalies detected with the operation of the airport surface detection equipment (ASDE) system. The Vancouver International Airport tower manager issued direction to staff to enter non-control-related information on flight progress strips in a box more appropriate than the taxiway designator box. NAV CANADA has proposed an amendment to Section RAC4.2.8 of the Aeronautical Information Manual (AIM), which would recommend that pilots include their location with the runway number when requesting take-off clearance.Safety Action Taken The Vancouver International Airport tower manager issued an Operations Bulletin on 04November2004 to remind controllers to adhere to the Air Traffic Control Manual of Operations (ATC MANOPS) direction to state the name of the intersection or taxiway when issuing taxi to position instructions or take-off clearances from an intersection. Controllers were also encouraged to specify the threshold used if more than one aircraft was being taxied to position. The Vancouver Control Tower Operations Committee conducted a review of the Operations Bulletin before its expiry date and a decision was made to let it expire without implementing any new procedure. The Vancouver International Airport tower manager issued direction to tower staff to document any anomalies detected with the operation of the airport surface detection equipment (ASDE) system. The Vancouver International Airport tower manager issued direction to staff to enter non-control-related information on flight progress strips in a box more appropriate than the taxiway designator box. NAV CANADA has proposed an amendment to Section RAC4.2.8 of the Aeronautical Information Manual (AIM), which would recommend that pilots include their location with the runway number when requesting take-off clearance. Although proposals have been made by Transport Canada and NAV CANADA to change the phraseology requirements regarding runway entry clearances for Air Traffic Services personnel and aircrew, the Board is concerned that a residual risk of collision remains until these proposals are implemented.Safety Concern Although proposals have been made by Transport Canada and NAV CANADA to change the phraseology requirements regarding runway entry clearances for Air Traffic Services personnel and aircrew, the Board is concerned that a residual risk of collision remains until these proposals are implemented.